An E&E Special Report

EARTHQUAKES:

Okla. scientist searches for small-quake triggers

To determine if an oil and gas wastewater disposal well is triggering earthquakes, an Oklahoma state seismologist is proposing a plan to resume operations and see if it provokes seismic activity.

Austin Holland, research seismologist with the Oklahoma Geological Survey, is trying to see if the injection well in southern Oklahoma can be conclusively linked to the spate of earthquakes.

"With careful monitoring, we should be able to definitively determine whether or not the earthquakes are induced and still provide enough conservatism to adequately protect public safety," Holland said.

Operations would stop if seismicity reached magnitude 1.8, Holland said, or even sooner if enough data become available. That is about the level of seismicity that is being felt by local residents in the wake of larger earthquakes in September.

The well near Ardmore, Okla., has been shut down since early October after state officials sharply limited operations in the wake of the rumbling.

Concerns about man-made earthquakes -- or "induced seismicity" -- have been growing in Oklahoma. The state Geological Survey and the U.S. Geological Survey recently warned that Oklahoma is in the throes of an "earthquake swarm," likely linked to injection (EnergyWire, Oct. 25). That prompted Oklahoma's insurance commissioner to recommend that residents buy earthquake insurance (EnergyWire, Oct. 31).

Injection at the Love County Disposal Well began two weeks before the earthquakes. Oklahoma has thousands of such wells, but not many have been drilled in the area of this well, called Love County Disposal No. 1.

Injection began Sept. 3 and the earthquakes started Sept. 17 in the area near the Texas border, about 100 miles north of Dallas. The strongest was magnitude 3.4, and they have damaged chimneys, broken windows and caused objects to fall in homes and businesses (EnergyWire, Oct. 2).

The Geological Survey moved four seismic stations into the area to determine more precise locations for the quakes.

The well was not hydraulically fractured. But a state report said it was treated with 10,000 gallons of hydrochloric acid.

Geologists have known for decades that deep injection of industrial waste can lubricate faults and unleash earthquakes. Some earthquake researchers now say the nation's drilling boom, fueled by advances in high-volume hydraulic fracturing, could be spurring a rash of such man-made quakes.

Most seismologists agree that the specific process of hydraulic fracturing, or fracking, presents little or no risk of triggering earthquakes that damage property or injure people.

Instead, they point to injection wells. Fracking and production of shale gas produce millions of gallons of wastewater. Some can be reused, but eventually, what comes to the surface must be disposed of. Usually, that's into injection wells.